In order to help determine the effectiveness of polling in a running
system it is usful to determine the ratio of how often the poll
function is called vs how often the completion is checked. For this
reason we add a poll_considered variable and add it to the sysfs entry
for io_poll.
Signed-off-by: Stephen Bates <sbates@xxxxxxxxxxxx>
---
block/blk-core.c | 8 ++++++--
block/blk-mq-sysfs.c | 4 +++-
include/linux/blk-mq.h | 1 +
3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 34ff808..14d7c07 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3307,19 +3307,23 @@ bool blk_poll(struct request_queue *q, blk_qc_t cookie)
{
struct blk_plug *plug;
long state;
+ unsigned int queue_num;
+ struct blk_mq_hw_ctx *hctx;
if (!q->mq_ops || !q->mq_ops->poll || !blk_qc_t_valid(cookie) ||
!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
return false;
+ queue_num = blk_qc_t_to_queue_num(cookie);
+ hctx = q->queue_hw_ctx[queue_num];
+ hctx->poll_considered++;
+
plug = current->plug;
if (plug)
blk_flush_plug_list(plug, false);
state = current->state;
while (!need_resched()) {
- unsigned int queue_num = blk_qc_t_to_queue_num(cookie);
- struct blk_mq_hw_ctx *hctx = q->queue_hw_ctx[queue_num];
int ret;
hctx->poll_invoked++;
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index fe822aa..ea8c3f5 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -176,7 +176,9 @@ static ssize_t blk_mq_sysfs_rq_list_show(struct blk_mq_ctx *ctx, char *page)
static ssize_t blk_mq_hw_sysfs_poll_show(struct blk_mq_hw_ctx *hctx, char *page)
{
- return sprintf(page, "invoked=%lu, success=%lu\n", hctx->poll_invoked, hctx->poll_success);
+ return sprintf(page, "considered=%lu, invoked=%lu, success=%lu\n",
+ hctx->poll_considered, hctx->poll_invoked,
+ hctx->poll_success);
}
static ssize_t blk_mq_hw_sysfs_queued_show(struct blk_mq_hw_ctx *hctx,
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e1544f0..7710f79 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -61,6 +61,7 @@ struct blk_mq_hw_ctx {
struct blk_mq_cpu_notifier cpu_notifier;
struct kobject kobj;
+ unsigned long poll_considered;
unsigned long poll_invoked;
unsigned long poll_success;
};
--
2.1.4
--
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